Binding agent for foundry cores and method of manufacture thereof



Patented June 4, 1940 UNITED STATES PATENT OFFICE BINDING AGENT FOR FOUNDRY CORES AND METHOD OF MANUFACTURE THEREOF No Drawing. Application April 5, 1938, Serial No. 200,129

12 Claims.

This invention relates to the manufacture of sand cores for foundry work and more particularly to a new and improved foundry core, a binding agent for such cores, and to the method of preparation thereof.

In the manufacture of cores for use in making metal castings, sand is mixed with various binders in different proportions, water is added to aid in holding the particles together in the green or unbaked state, the core is shaped. and then baked or dried. Among the more commonly used binders are linseed oil and other drying oils; core oils containing drying oils and rosin thinned with kerosene; cereal binders, such as, partially dextrinized starches which are water soluble; sulphite waste liquor residues; dextrin; pitches, such as, for example, coal tar; Bentonite, and other clays; molasses and other carbohydrate mixtures; rosin in powdered form and compound binders of various combinations of the foregoing.

All of the prior art binders mentioned have various disadvantages. Linseed oil, for example,

' although it has been widely used as a core binder,

does not readily mix with sand to which water has been added for proper temper" for forming into cores. Uniform mixtures are thus difficult to obtain, and often, after the cores are formed, the oil tends to settle to the lower part of the core or to migrate to the lower surface thereof producing a non-uniform care. In addition, linseed oil also produces large quantities of an irritant gas during the baking of the cores, as well as at the time of pouring of the metal.

Core oils have also been widely used, but one of the chief disadvantages of these is crystallization or separation of the components during storage. They are also water repellant, and, hence, do not mix well with moistened sand. As in the case of linseed oil, they also tend to. settle out of the cores, leaving a non-uniform core and losing efliciency.

Binders such as cereals, dextrins, starches, glues, llgneous binders and the like, possess the disadvantage of giving of! objectionable gases during the baking. Cores containing such binders are also characterized by low strength when dry and a tendency to absorb moisture from the air, thus,

' rapidly losing strength on storage.

A binder such as powdered rosin is difficult to maintain in powdered form, and also tends to soften under heat, so that cores handled while not will sag or run, and thus, be unfit for use. Powdered rosin is also sticky, consequently, it does not mix easily with the sand, and since it (Cl. 22-l88) is also water repellant, it does with the sand and water.

A binder such as pitch develops strength by the evaporation of the volatile matter and coking or hardening of the residue. A core containing a binder of this type has the disadvantage of raising the cleaning costs on the finished castings because such a core tends to harden more when the metal is poured in rather than to collapse, thus making it difficult to remove the core from the casting.

It is an object of this invention to provide a sand core binder which will overcome the objections above enumerated to drying oils, core oils, and other core binders commonly used, and which will yield a sand core which is more permeable, stronger, but at the same time readily collapsible under the heat of the casting, as well as producing less gas during baking.

I have found that I may overcome to a large extent the objections to prior art core binders by using as a binder gasoline-insoluble resin derived from pine wood, which has been modified with a glyceride oil or with the fatty acids derived from such oil with or without the addition of rosin or of a mineral oil, emulsified in disperse phase in water by means of a suitable emulsifying agent.

In the following description of my invention, I shall refer particularly to glyceride oils but it is to be understood that the fatty acids derived from such oils are also suitable and may be substituted therefor.

The gasoline-insoluble pine wood resin I employ in the preparation of my improved core binder and cores made therefrom, may be produced, for example, by extracting resinous wood with a coal tar hydrocarbon, removing said hydrocarbon by evaporation, leaving a residue comprising a mixture of wood rosin and the new 40 resin, extracting wood rosin from the said residue by petroleum hydrocarbon, leaving the new gasoline-insoluble pine wood resin, as described and claimed in application, Serial No. 61,745, filed not mix uniformly January 31, 1936, by Lucius C. Hall.

. 45 In preparing my emulsion core binder, I may, for example, proceed along the following lines.

Gasoline-insoluble resin derived from pine wood and a portion of the total glyceride oil are heated together until foaming subsides. After this ini- 50 tial cooking the remainder of the oil is added and the mixture re-heated until compatibility is obtained, the compatibility point being noted by observing a drop of the mix on glass. If this is cloudy on cooling, further heating is applied. By

the term compatibility of the ingredients as used herein, I mean that a combination of glyceride oil or fatty acid derived therefrom and the resin has been effected by the cooking of the ingredients 'so that when cool the ingredients do and will be dependent chiefly on the individual oil. Temperatures ranging from about 110 C. to about 350 C. have been used.

Alternatively, the resin and oil in proper proportions, may be heated together in one step instead of first heating the resin and a portion of the oil together and then adding the remainder of the oiland completing the cooking. Either method may be used, the choice of the particular method used depending primarily on the properties of the oil.

After the above cooking procedure, the oil and resin are in the form of a viscous dark colored material. This material, at a temperature preferably, although not necessarily, of about 90-110 C., is then emulsified in disperse phase in water containing a suitable emulsifying agent. I have found that satisfactory emulsions containing up to about 60% of dispersed phase may be readily prepared merely by the agitation provided by high-speed stirring. Emulsions prepared in this way will bestable and iiuid. If, however, finer emulsions are desired or, if it is desired to incorporate more than 60% of dispersed phase, I have found that a colloid mill or homogenizer is desirable. For most practical purposes, I prefer using an emulsion containing about dispersed phase, although as mentioned before, higher amounts can be satisfactorily dispersed to form stable emulsions which will dilute readily with water and form superior cores when admixed with sand.

The amount of gasoline-insoluble resin derived from pine wood and oil used may vary between quite wide limits. I have, for example, prepared compositions containing as high as 75% resin and 25% oil, which produced satisfactory, stable emulsions, although in some cases these were more viscous than those containing less resin. I have, also, prepared compositions containing as low as 10% resin and 90% oil, which still retained the combined binding effect of the two materials. In general, however, I prefer using about 50% or each.

I have also found that the addition of a mineral oil fraction to gasoline-insoluble pine wood resin-glyceride oil compositions, during, or after cooking, provides certain desirable qualities. It gives, for example, greater fluidity to the emulsion which means an improved ease of working in the ultimate core mix bonded with the emulsion. The addition of a mineral oil is, of course, optional and will depend upon the particular working qualities desired. In general, I prefer not to have over about 20% of the disperse phase present as a petroleum distillate, such as, for example, fuel oil. A fraction such as kerosene may be used, but in general a higher boiling fraction is desirable.

Glyceride oils in general are divided into drying, semi-drying and non-drying oil types depending upon their behavior when exposed to the air. Although the glyceride oils in general are operable in my process, for the best results I prefer using an oil of the drying or semi-drying type. Among the glyceride oils which I have insoluble pine wood resin,'triethanolamine, etc.

Of these emulsifying agents, I prefer using casein, put into solution by means of ammonium hydroxide. The casein may, however, be put into solution by means of other alkaline compounds among which are sodium hydroxide,

sodium carbonate, trisodium phosphate, borax, sodium bicarbonate, amines, etc. A procedure as follows is very satisfactory for making a casein solution which is free from lumps. Casein is first soaked for approximately 10 minutes in half of the total water to be used, to allow it to swell. The desired amount of ammonium hydroxide, for example, is then added, with stirring, to this casein solution. For complete solution the remainder of the water is added and the solution is stirred and heated to C.

When using casein as an emulsifying agent, I have found that from about 4% to about 15% by weight of the aqueous phase produces good results but for high stability and reasonable viscosity I prefer using about 8% by weight. In dispersing casein in water, a small amount of an alkaline compound is necessary. With ammonium hydroxide, which I prefer I may use from about 0.4% to about 2.0% by weight of the aqueous phase, of 29% aqueous ammonium hydroxide, preferably from about 0.75% to about 1.0% by weight of the aqueous phase. If substantially' more than 1.0% by weight of the aqueous phase of aqueous ammonia is used, the viscosity of the emulsion containing casein as an emulsifying agent increases rapidly. I have found it desirable, particularly in warm weather, to add a preservative to prevent mold growth or other bacterial action when usng casein as the emulsifying agent. For this purpose 0.1% to 5.0% by weight of the aqueous phase of a preservative such as sodium 2.4.5 trichlorphenate, phenol, etc. is very satisfactory, and is preferably added in water solution to the finished emulsion.

In some cases, it may also be desirable to add driers to accelerate the drying of the oil. This is effective not only with the drying and semidrying oil types but with the non-drying oils as well. The addition of about 0.02% manganese, by weight, of the oil, or an equivalent amount of either cobalt or lead has been found to be quite satisfactory. Manganese resinate, for example, can be readily incorporated into the hot resinoil composition during or after cooking, using about 1% of precipitated manganese resinate by weight of the oil.

In using my emulsion in the manufacture of a sand core, suitable for general foundry work, I prefer using the emulsion with sand in the ratio of about 1 part by volume of the emulsion to about 30-200 parts by volume of sand, depending upon such factors as the sand used, baking conditions, and type metal poured. By using sand of varying fineness, cores of various strengths may be obtained. Either wet or dry sand may be mixed with the emulsion to produce good cores when baked. I have found that cores made in accordance with this invention are occurs, and that the emulsion remains firmly held in position between and about the particles of sand. The binder, therefore, will not drop ltailed description thereof by reference to the a drop of the mix on glass.

following examples. All parts shown are parts by weight, unless otherwise indicated.

EXAMPLE 1 To 25 parts of gasoline-insoluble resin derived from pine wood there are added 10, parts'of linseed oil, and this mixture is then heated to about 300 C., and held there until foaming subsides. Afterthis initial cooking, the remaining 15 parts of linseed oil are added and the mixture reheated at about 300 C., until compatibility is obtained, the latter being noted by observing a To this hot mixture, after it iscompatible, there is added 0.25 part of manganese resinate. When the temperature of this reaction mixture has dropped to about 90 C. to 110 C., it is emulsified in an aqueous solution consisting of 45.35 parts of water, 4 parts of casein, and 0.4 part of 29% aqueous ammonia, by the use of a high-speed stirrer or, if desired, by passage thru a colloid mill. In-the latter case, I

have found that by pre-mixing the materials to a syrupy consistency, a fluid stable emulsion may be obtained after two passages through a Premier colloid mill. As a preservative, 0.4% of the aqueous phase of sodium 2.4.5 trichlorphenate may be added to the finished emulsion. This emulsion may then be admixed with sand for the preparation of a foundry core.

EXAMPLE 2 Thirty parts of gasoline-insoluble resin derived from pine wood, 15 parts of soya bean oil and 5 parts of mineral oil are heated together in the manner shown in Example 1. After compatability of the components has been attained and the reaction mixture has cooled to a temperature of about C. to C., it is emulsified in an aqueous solution consisting of 45.6 parts of water, 4 parts of casein and 0.4 part of 29% aqueous ammonia. 0.5% by weight of phenol based on the aqueous phase may be added to the finished emulsion as a preservative.

This emulsion may then be admixed with sand for the preparation of a foundry core.

EXAMPLE 3 Exempt]: 4

Thirty parts of gasoline-insoluble resin derived from pine wood, 15 parts of linseed oil and 5 parts of rosin are heated together as shown in Example 1. After the components are compatible and the reaction mixture has cooled to a temperature of about 90 C. -110 C. it is emulsified in an aqueous solution consisting of 48 parts of water and 2 parts of sodium oleate. Emulsions so produced may then be used as a binding agent for cores.

EXAMPLE 5 To 25 partsof gasoline-insoluble resin derived from pine wood, there are added 25 parts of castor oil and the mixture heated to C. where the components become compatible. When the temperature of this reaction mixture has dropped to about 100 C. it is emulsified in 50 parts of an aqueous solution consisting of 8% by weight of casein, 0.6% by weight of 29% ammonium hydroxide and 91.4% of water, by passing twice through a Premier colloid mill. As a preservative for the casein 0.25%. phenol by weight of the aqueous phase was added to the finished emulson.

A very satisfactory core may be made by admixing 1 part by volume of this emulsion, 2 parts by volume of water and 40 parts by volume of Manistee sand and baking at 425% .F. for 1 hours.

EXAMPLE 6 Twenty-five parts of gasoline-insoluble resin derived from pine wood and 25 parts of peanut oil are heated to about 330 C. to obtain compatability. After the components are compatible, an emulsion is prepared in the same way as shown in Example 5.

A high quality sand core may be prepared using the proportions shown in Example 5.

The emulsion binder prepared in the manner indicated above has superior binding properties for sand in the making of cores. 1 believe that its superiority in this respect lies in its greater penetration or extensibility throughout the sand, thus, coating the grains of sand uniformly with a coating of binder easily miscible with water. The emulsion may, therefore, be as readily mixed with wet sand as with dry sand, resulting in a uniform effect throughout the core. Furthermore, during the baking of the cores, containing as a binder the emulsion made as shown above, there is very low gas formation, which also holds true when the core is subjected to the heat of the metal during the casting operation. Although a sand core made with my binder is stronger than many cores made with prior art binders, it also possesses the highly desirable quality of collapsing readily, after the casting has been poured. My emulsion core binder has the qualities of permitting rapid baking of cores without sacrificing any essential qualities, it also possesses some fgreen bond, and because of the presence of gasoline-insoluble resin derived from pine wood, the oil does not separate out and is retained by the cores.

It is also possible to use other binders such as cereals, sulphite residues, pitches and the like in combination with my emulsion binder to produce cores having certain desired specific properties.

It will be understood that the examples shown above are by way of illustration only and that no limitations are intended thereby, except as hereinafter embodied by the scope of the claims.

What I claim and desire to protect by Letters Patent is:

1. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and a substance selected from the group consisting of glyceride oils and the fatty acids derived therefrom, at a temperature and for a period of time sufficient to obtain compatibility of the ingredients, emulsified in disperse phase in water with an emulsifying agent.

2. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood, rosin and a substance selected from the group consisting of glyceride oils and the fatty acids derived therefrom at a temperature and for a period of time sumcien't to obtain compatibility of the ingredients, emulsified in disperse phase in water with an emulsifying agent. I

3. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and a drying oil at a temperature and for a period of time suflicient to obtain compatibility of the ingredients, emulsified in disperse phase water with an emulsifying agent.

4. A binding agent for foundry sand cores comprising essentialiy the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and a semi-drying oil at a temperature and for a period of time sufficient to obtain compatibilityof the ingredients, emulsified in disperse phase in water with an emulsifying agent.

5. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and linseed oil at a temperature and for a period of time sufficient to obtain compatibility of the ingredients, emulsified in disperse phase in water with an emulsifying agent.

6. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and oiticica oil at a temperature and for a period of time sufficlent to obtain compatibility of the ingredients, emulsified in disperse phase in water with an emulsifying agent.

7. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin de- ,rived from pine wood and soya bean oil at a temperature and for a period of time sufiicient to obtain compatibility of the ingredients, emulsified in disperse phase in water with an emulsifying agent.

8. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and a glyceride oil at a temperature and for a period of time sufficient to obtain compatibility of the ingredients, emulsified in disperse phase in water with casein dissolved therein by means of an alkaline compound.

9. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and a glyceride oil at a temperature and for a period of time sufiicient to obtain compatibility of the ingredients, emulsified in disperse phase in an aqueous solution of casein containing ammonium hydroxide, said aqueous solution containing from about 4% to about 15% by weight of casein and from about .4% to about 2% by weight of 29% aqueous ammonium hydroxide.

10. A binding agent for foundrysand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and a glyceride oil at a temperature and for a period of time sufficient to obtain-compatibilityof the ingredients, emulsified in disperse phase in water with sodium oleate.

11. A binding agent for foundry sand cores comprising essentially the reaction product obtained by cooking together gasoline-insoluble resin derived from pine wood and a. glyceride oil at a temperature and for .a period of time sufficient to obtain compatibility of the ingredients, emulsified in disperse phase in water with an emulsifying agent, the said oil being in amount within the range of about 25% to about by weight of the disperse phase.

12. The method of making a binding agent for foundry sand cores which comprises cooking together gasoline-insoluble resin derived from pine wood and a substance selected from the group consisting of glyceride oils and the fatty acids derived therefrom, at a temperature and for a period of time suflicient to obtain compatibility of the ingredients and emulsifying said reaction product in disperse phase in water with an emulsifying agent.

PHILIP A. RAY. 

